1. Field of the Invention
The present invention relates to a vessel propulsion apparatus that propels a vessel and a vessel that includes the vessel propulsion apparatus.
2. Description of the Related Art
U.S. Pat. No. 7,704,111 discloses a vessel propulsion apparatus with which an exhaust is purified by a catalyst. This vessel propulsion apparatus includes the catalyst that purifies the exhaust, an exhaust manifold that houses the catalyst, and a water pump that supplies cooling water to a water jacket provided in the exhaust manifold.
As shown in FIG. 7 of U.S. Pat. No. 7,704,111, the exhaust manifold includes a first exhaust passage 39C collecting the exhaust discharged from outlets of respective exhaust ports and a second exhaust passage 40C disposed further downstream than the first exhaust passage 39C. The catalyst 42 is disposed inside the second exhaust passage 40C. As shown in FIG. 8 of U.S. Pat. No. 7,704,111, the water jacket 57C is provided along the first exhaust passage 39C and the second exhaust passage 40C. As can be understood from FIG. 3 of U.S. Pat. No. 7,704,111, the catalyst 42 is surrounded by the water jacket 57C.
A vessel propulsion apparatus that includes a catalyst generates more heat than a vessel propulsion apparatus that does not include a catalyst. The vessel propulsion apparatus including the catalyst must thus have a high cooling ability.
One method for providing a vessel propulsion apparatus with a high cooling ability is to increase the capacity of the water pump that takes in water from outside the vessel propulsion apparatus. However, a high-capacity water pump has a large size, and there are cases where the capacity of the water pump cannot be increased to the necessary capacity due to restrictions in the internal space of the vessel propulsion apparatus in which the water pump is disposed.